Polymethylbenzene treating process



July 19, 1960 D. E. BowN Erm.'

POLYMETHYLBENZENE TREATING POCESS Filed March 25, 1957 vUnited States Patent() POLYMETHYLBENZENE TREATING PROCESS Delos E. Bown, Baytown, Harold W. Earhart, Houston, and Robert H. Perry, Jr., and Daniel E. Nicholson, Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, NJ., a corporation of Delaware Filed Mar. 25, 1957, Ser. No. 648,353

8 Claims. (Cl. 260-668) f, This invention relates to a process for treatment of polymethylbenzene hydrocarbons for the production of durene. More particularly, the present invention relates to a process for the preparation and recovery of durene from` polymethylbenzene feed stocks containing an average of about 8.5 to about 9.5 carbon atoms per molecule.

' It has been discovered in accordance with the present invention that when a polymethylbenzezne feed stock con-l taining an average of from about 8.5 to 9.5 carbon atomsl per molecule is reacted with about lrmol of a'methylating agent per mol of feed stock in the vapor phase in the-pres-v ence of a silica-alumina alkylation catalyst at a temperature Within the range of about 650'? to 950 F. at a liquid flow rate of about V0.2 to l v./V./hr.Y there is formed a polymethylbenzene product containing an enhanced amount of durene.

i `During the course of the treatment, a wide variety of reactions take place, including methylation reactions, disproportionation reactions, and transmethylationreactions.

A feature of the present invention is the discovery that under the aforesaid reaction conditions a transmethylation type series of reactions occurs which have the net effect of convertingtrimethylbenzenes and hexamethylbenzene` toi dimethylbenzenes and tetramethylbenzenes. `A particularly desirable feature of the present invention Yis that the products from the aforesaid reactions exist in an equilibrium state such that the reaction product contains a minimized amount of benzene, toluene, penta- 2,945,899 Patented Jslylfe 1969.

ice

` tion agent per mol of feed stock. Among the methylating methylbenzene, and hexametnylbenzene, whereby it is possible to recycle such components to the reaction zone without undesirable effects in that such components tend to be converted to `C8 to C10 polymethylbenzenes. As a consequence, the process of the present invention is parl Catalysts to be employed in accordance with the present i `invention are silica-alumina catalysts which preferably contain from about 5 to 25 weight percent of alumina. Although the surface area of the catalyst may be varied within wide limits, it has been discovered in accordance with the present invention that unexpectedly superior yields of durene are obtainable when the surface area of the catalyst is within the range of about 100 to 200 m.2/gm. Y

`The feed stock of the present invention should be a polymethylbenzene feed stock which is-preferablyA substantially completely free from oleiinic components and which contains an average of from about 8.5 to 9.5 carbon atoms per molecule. Thus, the feed stock to the reaction zone may/'comprise a mixture of `C7 to C12 poly- V methylbenzene components, such components being pro' portioned in a manner such that there'is an average ofI 8.75 to 9.5 carbon atoms per molecule of feed stock. Preti agents that may be used with good results are compounds such as methyl chloride, methyl alcohol and dimethyl ether.

The methylating agent and feed stock are brought into contact with the silica alumina catalyst in vapor phase at a temperature within the range of about 650 to 950 F. at a velocity, computed on the basis of liquid flow rate, of from about 0.2 to about l v./v./hr. In general, methyl chloride is the preferred methylating agent at temperatures of from about 650 to about 750 F. in that the best yield of-durene is obtained with methyl chloride within this temperature range. At temperatures interi mediate about 750 to 950 F. the durene yield is en-` hanced through the use of an oxygen-containing methylat ing agent such as methyl alcohol or dimethyl ether. i

It is desirable to correlate reaction temperature-with flow rate, owrate being increased as temperature is" infY creased. Thus, at temperatures of about 650 to 750? F., it is preferable to employ a liquid llow rate of about 0.2 to about 0.5 volume of feed per volume of catalystl per hour. At temperatures intermediateV 750 'to 950 F. it is preferable to employ a flow rate of about 0.5 to 1.0 `volume of feed per volume of catalyst per hour. v

.The reaction is preferably conducted at atmospheric pressure but, if desired, higher pressures of up to about 500 p.`s.i.g. may be employed.

A In conducting the process of the present invention in a continuous manner, a mixture of a suitable feed stock and carbon components which are discarded and a polymethylbenzene fraction. The polymethylbenzene fraction is treated in any suitable manner such as'by avcombination distillation and fractional crystallization process to be described subsequently to recover durene as a product afterwhich the remainder of the polymethylbenzenes are recycled to the conversion zone. A preferred manner in which lthe process of the present invention may be practiced in a continuo-us manner-is diagrammatically disclosed in the single figure ofthe attached drawing, such showing being given by way of illustration and not being intended as a limitation on the scope of this invention. Y Turning now to the drawing, there is disclosed a charge line `10 containing a .pump l2 leading to a preheater 18.4 The preheater 18 is connected with a reactor 20 containing a bed of silica-alumina catalyst by way of a line 22 containing a pump 24. A suitable polymethylbenzene feed stock such as, for example, pseudocurnene, is delivered to the linelt) from a suitable source (not shown). A recycle material obtained in a manner to be described is added to.

ture, Ithe methylating agent being charged to the line 10 from a storage tank 2S by Way of a linetl containing a" pump 32.

. The resultant mixture is passed by the line 10 to preheater 18 wherein the feed mixture -is brought to a reaction temperature within the range of about 650 to about 950 F.

The vaporized feed components are then passed by way of the line 22 to the reactor 20 at a liquid ow rate within the range of about 0.2 to about 1.0 volume of feed mixture per volume of catalyst per hour.

Within the reactor 2d at least a portion of the methylating agent reacts with polymethylbenzene feed mixture components to form methylation products and, in addition, disproportionation and transmethylation reactions also occur whereby a product is formed containing a wide variety of polymethylbenzenes, a small amount of normally gaseous hydrocarbons and whereby carbonaceous deposits are also laid down on the bed of catalysts. The catalysts may be periodically regenerated as desired by controlled combustion of the carbonaceous deposits by any of the suitable regeneration techniques known to those skilled in the art.

In the case where the methylating agent is methyl chloride the reaction products are discharged from reactor 20 by way of a line 34 containing a pump 36 and controlled by a valve 38 leading to an incorporator 40 of any suitable construction such as a bathed type incorporator. Within the incorporator 4i) the reaction products are intimately mixed with a suitable wash liquid, such as water introduced by way ot a line 42. The thus-formed mixture is discharged from the incorporator 4t) by way of a line 44 leading to a settler 46 wherein the water and dissolved hydrochloric acid by-product separate from the reaction products for discharge by way of the line 4S. The water washed product is withdrawn from the settler 46 by way of a line 5t) containing a pump 52 leading to a second incorporator 54 of any suitable construction such as a bathed type incorporator, wherein the water washed product is mixed with an alkaline wash solution such as an aqueous solution of sodium hydroxide introduced thereto by way of a charge line 56 controlled by a valve 58. The purpose of the caustic wash step is to remove trace amounts of hydrogen chloride and other acidic contaminants which may be present in the reaction products. The thus-formed mixture is discharged from incorporator 54 by way of a line 60 leading to a settler 62 wherein phase separation occurs, the spent alkali solution collecting as a liquid phase and being withdrawn from the settler 62 by way of a discharge line 64 controlled by a valve 66. lf desired, all or a part of the spent caustic solution may be recycled to the `charge line 56 leading to the incorporator 54 by way of a recycle line 68 controlled by a valve 70.

The treated reaction products are withdrawn from the settler 62 by way of a line 72 controlled by a valvef74 leading to a separation zone comprising suitable means such as a plurality of fractionators 76, 78'and 80 for fractionating the reaction product into desired fractions.

For example, the reaction product fed to the fractionator 76 by way of the line 72 may be split into a gaseous hydrocarbon fraction taken overhead from. the fractionator 76 by way of a line S2 for discard and a side stream fraction consisting essentially of methyl chloride discharged by way of a branch line 84 containing a pump 86 leading to the methyl chloride storage tank 28.

A bottoms fraction consisting essentially of polymethylbenzenes is discharged from the fractionator 76 by Way off a bottoms line 88 containing a pump 90 leading to the fractionator 78. Within the fractionator V78 the polymethylbenzenes are split to form an overheads fraction discharged by way of aline 92 containing a pump 94 leading to the recycle line 26, the overhead fraction .92 consisting primarily of polymethylbenzenes containing less than carbon atoms.

A polymethylbenzene fraction containing C10 and heavier polymethylbenzenes is discharged from the fractionator 78 by way of a line 96 containing a pump 98 leading to the fractionator 80 wherein anoverhead fraction consisting essentially of tetramethylbenzenes is ob-I tained as an overhead fraction discharged by way of the line 100 containing a pump 102. A bottoms fraction containing reaction components of more than l0 carbon atoms is discharged from the fractionator by way of a bottoms discharge line 164 containing a pump 106 which also leads to the recycle line 26.

The tetramethylbenzene fraction taken overhead from the fractionator Sti is charged to a suitable durene recovery zone such as a fractional crystallization zone 11d wherein substantially pure durene is recovered. Purhied durene is discharged from the fractional crystallization zone by a line 112 as product and the remainder of the tetramethylbcnzene fraction is discharged from the fractional crystallization zone ll by a discharge line 114 containing a pump 116 leading to the said recycle line 26.

It will be understood, of course, that if desired other valuable polymethylbenzenes such as paraxylene, mesitylene, etc., may also be recovered from the products ofV the reaction prior to the recycle of the undesired polymethylbenzene components by way of the line 26 to the charge line 10.

In the situation wherein the methylating agent is an oxygen-containing methylating agent, such as methyl alcohol or dimethyl ether, the principal by-product is water, the reaction product being substantially free from corrosive reactive by-products as is the case where methyl chloride is employed. In this situation, therefore, the valve 38 in discharge line 34 from reactor 20 may be closed and the valve 74 in the charge line 72 for the fractionator 76 maybe closed whereby the settlers 46 and 62 are `bypassed. In this situation, the eluent from the reactor 20 passes from the discharge line 34 to a branch line 118 controlled by a valve 119 to settler 120. The water in the ,reactor eiuent is condensed and separated from the remainder of the products in the settler 120 and discharged therefrom, by a line 122. The remainder of the products are discharged from the settler 120 by way of a line 124 controlled by a valve 126 leading to the charge line 72 for the fractionator 76. The efuent is thereafter processed in the described manner.

As a specic example, a suitable feed stock such as, for example, pseudocumene may be continuously processed for substantially complete conversion to durene. For example, barrels per day of pseudocumene of 95% purityl may be introduced into the charge line 10 for conversion to durene. The pseudocumene may be mixed with recycled polymethylbenzenes and about 1v mol of methyl chloride per mol of said mixture to form a total charge of about 783 barrels per day of feed mixture charged to the reactor 20 by way of drier 14 and the preheater 18. About 775 barrels per day of liquid products plus hydrogen chloride, gaseous hydrocarbons and methyl chloride are discharged from the reactor 20 by way of the line 34 as ei'rluent. Theeiuent is water Washed in the incorporator 40 and the wash product is withdrawn from the settler 46 for treatment with a suitable alkali in the line 50, the treated etiluent being discharged from the settler 62 by way of the line 72 leading to the fractionator 76. Unreacted methyl chloride (normally amounting to about 50 volume percent of the methyl chloride charged) is discharged from the fractionator 76 by way of the branch line 84 for return to the methyl chloride storage tank 28. As indicated, about 775 barrels per day of polymethylbenzenes are taken as a bottoms fraction from the ractionator 76 by way of the line 38. The polymethylbenzenes are split in the fractionator 7 8 into a bottoms traction of polymethylzenzenes containing at least l0 carbon atoms per molecule at the rate of about 385 barrels per day. An overhead fraction consisting of C9 polymethylbenzenes and lighter polymethylbenzenes at the rate of about 389 barrels per day is taken overhead by way of the line 92 and charged to the recycle line 26. The bottoms fraction 96 from the fractionator 78 is split in the fractionator 80 into about Space Velocity, v./v./hr

. 250 barrels per day of tetramethylbenzenes taken overhead by way of the line 100 and about 136 barrels per day of pentaand hexamethyl kbenzenes discharged by the line 104 leading to the recycle line 26. v

The tetramethylbenzenes are charged byway of the i vvertedto durene and that only about 8% is'lost-from the process in the form of by-products.

The present'invention will be further illustrated bythe following specific examples which are given by way of illustration and which are not intended as limitations on the scope ofthe invention.

EXAMPLE I VF. to form a catalyst having a surface area 'of about 122 111.2/ gm. The reaction conditions employed and the results obtained are set forth in the following table.

Table I Feed Stank Pseudocumene Methylatng Agent. Mol Ratio of Feed Stock to Methylating Agent.-- Temperature, "F

Total Fraction of Methylating Agent Converted to Methylbenzenes percent-- Conversion to Liquid Product ..do Amount of Durene in Tetramethylbenzene Fraction .percent-- v From Table I it will be seen that in each instance a substantial yield of teteramethylbenzenes was obtained, about one-third of the tetramethylbenzene fraction consisting of durene. It is to be observed that the primary products of the reaction were trmethylbenzencs, tetramethylbenzenes and pentamethylbenzene, and thatonly a very negligible amount of xylenes and hexamethylbenzene were formed.

It is to lbe further observed that there was a substantially `complete lconversion of the pseudocumene to liquid products, a V95% conversion being obtained with methyl chloride and a 97.5% conversion being obtained with methyl alcohol. Y

Itis a characteristic of the present invention thatV not allv of thef'methylating agent is reacted withthe polymethylbenzene feed stock as is shown by the fact .that there was only about a 50 volume percent conversion with respect to the methyl chloride run and a 48 volume percent conversionpwith respect to the methyl alcohol run.

.p6 v EXAMPLE n As has been indicated, it is preferable to employ silicaalumina catalysts having a surface area of from about 100 to 200A m.2/gm. This is shown by the results of the Table II Y Feed Stock Pseudocumene Run. No Y -1 2 3 i l Methylating Agent CHsCl CHaOH CHgOH CHSOH Mol Ratio of Feed Stock to Methylating Agent 1/1 1/1 1/1 1/1 Temperature, F 700 900- 1 000 700` Space Velocity, v./v./hr 0.39 0.67 0.33 O. 33

Product Composition: I

Benzene 0.0 0.0 0.0 0.0 Toluene- 0. 0 0. 8 0. 9L 0. 0 Xylenes 2.2 3. 8- 12. 6 1. 1 Trimethylbenzenes. 70.6 66. l 54. 0 70.] Tetramethylbenzen 18. 9 22. 4 28. 2 15. 7 Pentamethylbenzene 6.2 5.9 3.6 4.1 Hexamethylbenzene 2.0 1.3 v 0.2 3.4

Total 99. 9 99. 8 99. 5 101;'0

Fraction of Methylating Agent Converted to Methylbenzenes percent.- 20 27 15 26 Conversion to Liquid Product---;.' -pereent.- 91 S8 88 90 Amount of Durene in Tetra- Y methylbenzene Fraction percent.. 33 35 35 l 33 When the results of runs l and 2 of Table II are cornpared with the results of Table I, it will be observed that there was a substantial diminution of yield when a high surface area catalyst was employed as in Example II. Thus, with methyl chloride it will be observed that the yield of teteramethylbenzenes Was only about 19% as contrasted with the 26% yield in the case of Example I. vIt is further to be noted that the conversion of methyl chloride to polymethylbcnzenes was substantially less in the case of Experiment .II and that the yield of liquid products was substantially lessened both with respect to the methyl chloride run andrwith respect to the methyl alcohol run.

Runs 3 and 4 of Table II are demonstrative of the 'influence of temperature and ow rate on reaction product compositions and conversion. Thus, in the case of run No. 3 pseudocumene was treated with methyl alcohol vat 900 F. and a new rate of about 0.3 v./v./'hr. (approximately twice as long a contact time as in the case of run No. 2). =It will be observed that the slightly increased yield of tetramethylbenzenes was more than oiset by the increase in xylenes formation. In run No. 4 wherein-the methyl alcohol was reacted with pseudocumene ata temperature of 700 F. and a flow rate of 0.33 v./v.hr. (essentially the reaction conditions of run No. 1) there was a substantial diminution in the yield of tetramethylvbenzenes as compared with the resultsobtained in run No. 2.

EXAMPLE III As further examples of the process of the present invention, samples of pseudocumene of purity were treated with methyl alcohol and dimethyl ether in the presence of a catalyst consisting of about 87 weight percent of silica and 13 weight percent of alumina, such catalyst having a surface area of about 200 m2./gm. Reaction conditions employed and the results obtained are set forth in Table III.

`Experiment Number 36 l'37 38 VMol `Ratio `Methylating Agent "to A`Pseudocunue1'1e -1/1 1/1. 1/1 Reactor Temperature "F 700 900 900 Liquid Flow Rate, 'v./v./tir 0:30 0. 30 0.' 30 Mthylating Substance CHSOH .CHQOH (CH'QMO 'ProductaCompositiom Wt., Perce Total Cs Aromatics v 1 9 A23.0 9.9

'Pseudooumene 33. 4 23. 7 31. 4 Mesitylene 7.0 11. 2 .10.54 Hemimellitene Y' u A '4.7

vIotalCg Aromatics MAAf1 3 .377.5v 46.5

Prehnitene K 6. 5` 7. 5. 3. 3

Total C1.) Aromatics 37. 9. a3. o 31.6

j Pentamethylbenzene 9.3 `3.,0 5. 4 Hexamethy1benzene 4; 2 i 0. 8 4. 8

From Table III it will be observed that in each instance "there was a substantial conversion of pseudocumene, .from about 12 to 14 percent of the polymethylbenzene "product consisting "of durene.

EXAMPLE IV Table I V Temperature F :700 Flowrate, v./v ./'hr 10:39

Composition Feedl Stock Product LBenzene... I0.0 `0 0 :Toluene 0. 0, D. 4 Xylenes 3.2 5. 0 .Trimethylbenzenes. 61.0 `51; 6 Tetramethylbenzenes Y2,5. 5 33. 4 Pentamethylbenzene..- 6. 6 '8. I) .-Hexamethylbenzne. -'3. 6` 1. 6

jFrom Table IV it will bessen that there was a sigm'ii- "cant reduction in trime'thylbenzene and hexamethylbenzene-content when the feed stock is compared to the lproduct, the net effect being to substantially increase Athe tetramethylbenzene content-ofthe product.

Having f described our invention, what is/ claimed is:

1. A process which comprises treating a polymethylbenzene feed stock containingan average of from about 8.5 to 9 5 carbon atoms per molecule in a combination methylationydisproportionation and transmethylation reaction zone with about l mol of a methylating agent per mol of feed stock in vapor phase at about atmospheric pressure in the presence of a silica-alumina alkylation 'catalyst -at a temperature within the range of about 650 'to 950 F. at a liquid llow rate of about 0.2 to l v./v./hr.

tion.

2. A "process -`s in 'claim -1 wherein 'the methylating agent?sinethyl 'chloridefand -wherein the" treatin'gi condi- 'Ations `include a temperature 'within the range of "about 650 to 750 F. andailiquid Vilow `rate=within thefra'n'ge of abouti`0.2`to aboutiOS `v./v./hr. l

Y f3. `A method as in claim 1 wherein the methylating 'agent isA methyl alcohol and wherein fthe treating conditions includelatemperature of about '750 to 950 yF. -andfa liquidow rate within the rate of about 0.5 lto about 1' v./v.'/hr.

4. A method as in claim l wherein the'methylating agent is dimethyl "ether and wherein the' treatingcondi- "tionsinclu'de a'temperaturelof about 750 to 950 'and ia'liquidfilow ratewithin the 'rate of 'about "0.51to about 1 v./v./hr.

A y'5. A method'v which comprises the" steps of'vcontinuously chargingy toa conversion 'zone containing arsilica-aluniina catalyst l a Vaporized 'v mixture o f polymethylbenzene feed stock containing an averageof :from about 8.5 `to 9.5 carbon atoms per molecule in a combination methylation, disproportionation and transmethylation reaction zone with about .1 :mol'of methylating ageutpermol of Yfeed stock-atfa'temperature within the range-ofabout 650 `to 'about950 LF. lataliquid low-rate'within the range of 4aboutOtZ tofabout l v.`/v.'/hr., 'and about y'atmospheric pressure withdrawing the lproducts 'of said reaction ffroin vksaid conversion :zone land separating -said `products into a gaseous .hydrocarbon fraction, a methylation agent fraction, Aand apolymethylbenzene fraction, recovering durene-from saidvpolymethylbenzene 'fraction and Iconltinuously directly frecylcing 'the y remainder of i said poly- 'fmethylbenzene'fractionto saidfconversion zone as at least a portion of said-'feed'=s`to'ck.

6. A process for the preparation of durene which comprises charging a mixture of pseudocumene and a polymethylbenzene recycle fraction to a combination methylatiom disporportionation and 4transrnethylation reaction zone conversion Vzone containing-a bcdo rsilicaalumina' catalyst having `a Vsurface area within the range ofrabout tovZOOm/gm. in vaporphase'in admixture Withabout 1 mol of methyl chloride per mol of feed mixture at a-temperature within the range of about 650 to 750 F. at a flow rate of about0.2 `to 0.05 v./v./hr. and about'atmospheric -pressure,-continuously washing the product of saidreaction with waterto remove byfproduct-hydrogenchloride, continuously neutralizing the water washed product with an aqeous alkaline solution, next continuously fractionating said product to obtain a gaseous hydrocarbon product, a methyl chloride Vproduct fraction and a polymethylbenzene product fraction, continuously fractionating said Vpolymethylbenzene fraction in a fractionation zone into a -rst fraction consisting of polymethylbenzenes containing less than .l0 .carbon atoms, a second .fraction consisting essentially of tetramethylbenzenes and a third fraction consisting essentially of polymethylbenzenes containing more than about 10 carbon atoms per'mole'cule, continuously' treat- 'ing said second fraction to obtain a high purity 'durene product vand va Vfourth fraction containing a reduced amount of durene and continuously vdirectly recycling said 'rst, third V"and fourth 'fractions to'said conversion'zone as said'recycleV fraction.

7. A process for Vthe preparation of durene which comprises charging a mixture of pscudocumene and a polymethylbenzene fraction'toa'cornbination` methylation, 'disproportionation'and transmethylation `rea'ctiorrzo'ne conversion 'zone 'containinga bed of silica alumina cata-- lyst having 'a surface ar'eawithin'thc range of about 100 to 200 m.2/grn. in vapor phase in adrnixturewith oout`1 mol of methyl alcohol'per'molV of'feed'mixture at'a temperature within'the range ofabout 750 to about950" F. at aflow rate of vvabout 0.5 to 1 v./v./hr. and about atomspheric pressure, continuously separating by-product waterfromsaid reactionproduct, next continuously fractionatingisaidproductitoobtaina gaseous hydrocarbon a high purity durene product and `a fourth fraction con-l taining a reduced amount of durene and continuosuly directly recycling said Yrst, third, `and fourth, fractions to said conversion zone Vas said recycle fraction.

8. A processfor the preparation of durene which comprises charging a mixture of pseudocumene and a polymethylbenzene fraction to a combinationmethylation,

hydrocarbon product, a product fraction, a dimethyl ether product and a polymethylbenzene product fraction, continuously fractionating said polymethylbenzene fraction in a fractionation zone into a rst fraction consisting of polymethylbenzenes containing less than l carbon atoms, a second fraction consisting essentially of tetramethylbenzenes, and a third fraction consisting essentially of polymethylbenzenes containing more than about carbon atoms per molecule, continuously treating said second fraction to obtain a high purity durene product and a fourth fraction containing a reduced amount of durene and continuously directly recyling said y flrst, third, and fourth fractionstosaid conversion zone disproportionation andrtransmethylation reaction zone t conversion-zone containing a bed of silica-alumina catalyst having a surface area within the range of about 100 to 200 mil/gm. in vapor phase in `admixture with about `1 rfnol of dimethyl ether p er mol of feed mixture at a temperature within the range of about 750 to about 950 F. ata ow rate of about 0,5 to 1 v./v./hr. and about atmospheric pressure, continuously separating byproduct water from said reaction product, next continuously fractionating said product to obtain a gaseous as said recycle fraction.

References Cited in the lle of this patent UNITED STATES PATENTS Australia July 7, 1955 

1. A PROCESS WHICH COMPRISES TREATING A POLYMETHYLBENZENE FEED STOCK CONTAINING AN AVERAGE OF FROM ABOUT 8.5 TO 9.5 CARBON ATOMS PER MOLECULE IN A COMBINATION METHYLATION, DISPORPORTIONATION AND TRANSMETHYLATION REACTION ZONE WITH ABOUT 1 MOL OF A METHYLATING AGENT PER MOL OF FEED STOCK IN VAPOR PHASE AT ABOUT ATMOSPHERIC PRESSURE IN THE PRESENCE OF A SILICA-ALUMINA ALKYLATION CATALYST AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 650* TO 950*F. AT A LIQUID FLOW RATE OF ABOUT 0.2 TO 1 V./V./HR. AND RECOVERING DURENE FROM THE PRODUCTS OF SAID REACTION. 